S 
i,  E.  S.  Library  -  GOP.  %  ' 

CONNECTICUT  ^      ^  ^' 

AGRICULTURAL  EXPERIMENT  STATIOE  " 

NE^V     HAVEN,     CONN. 


BULLETIN   165,  NOVEIVIBER,    1909. 


ENTOMOLOGICAL  SERIES,   No.   15. 

The  San  Jose  Scale  and  Methods  of 
Controlling  It. 


Fig.   I. — San  Jose  Scale  on  apple  bark.     Natural  size. 
CONTENTS. 

PAGE 

Officers  and  Staff  of  Station 2 

The  San  Jose  Scale  and  Methods  of  Controlling  It 3 

Introduction  into  the  Eastern  States 3 

Discovery  and  Spread  in  Connecticut 3 

Nursery  Inspection  and  Legislation 5 

General  Appearance  of  the  Insect 6 

Effect  upon  Trees 8 

How  the  Scale  Spreads  from  Tree  to  Tree 8 

Life  History  of  the  San  Jose  Scale 10 

Food  Plants i  r 

Natural  Enemies 13 

Control  Measures 16 

Fumigating  Nursery  Stock 16 

Spraying  Orchard  Trees ;  17 

How  to  Treat  an  Infested  Orchard 22 

Summary 24 

The  Bulletins  of  this  Station  are  mailed  free  to  citizens  of  Con- 
necticut "who  apply  for  them,  and  to  others  as  far  as  the  editions 
permit. 


CONNECTICUT  AGRICULTDRAL  EIPERIMENT  STATION. 


BOARD   OF  CONTROL. 

His  Excellency,  Frank  B.  Weeks,  Ex  officio.  President. 

Prof.  H.  W.  Conn,  Vice  President Middletown. 

Prof.  W.  H.  Brewer,  Secretary New  Haven. 

George  A.  Hopson Wallingf ord. 

Charles  M.  Jarvis Berlin. 

Frank  H.  Stadtmueller Elmwood. 

J.  H.  Webb Hamden. 

E.  H.  Jenkins,  Director  and  Treasurer New  Haven. 


STATION   STAFF. 

Chemists. 

Analytical  Laboratory. 

John  P.  Street,  M.S.,  Chemist  in  Charge. 

E.  Monroe  Bailey,  M.S.  C.  B.  Morrison,  B.S. 

R.  B.  Roe,  A.B.  C.  E.  Shepard. 

Laboratory  for  the  Study  of  Proteids. 
T.  B.  Osborne,  Ph.D.,  Chemist  in  Charge. 

Botanist. 
G.  P.  Clinton,  S.D. 

Entomologist. 
W.  E.  Britton,  Ph.D. 

Assistant  in  Entomology. 
B.  H.  Walden,  B.Agr. 

Forester. 
Samuel  N.  Spring,  M.F. 

:  Seed  Testing. 

Mary  H.  Jagger. 

Stenographers  and  Clerks. 

Miss  V.  E.  Cole. 
Miss  L.  M.  Brautlecht. 
Miss  E.  B.  Whittlesey. 

In  charge  of  Buildings  and  Grounds. 
William  Veitch. 

Laboratory  Helper. 
Hugo  Lange. 

Sampling  Agent. 
V.  L.  Churchill,  New  Haven. 


THE   SAN   JOSE    SCALE   AND   METHODS    OF   CON- 
TROLLING   IT.* 

By  W.  E.  Britton,  State  Entomologist. 

No  other  insect  has  caused  so  much  destruction  in  fruit 
orchards  throughout  the  country  as  the  San  Jose  Scale  (Aspidio- 
tus  perniciosus  Comst.).  This  scale  was  first  noticed  by  fruit 
shippers  near  San  Jose,  Cal.,  and  was  described  by  Prof.  J.  H. 
Comstock,  in  1880.  It  was  at  that  time  doing  much  damage  in 
California,  and  Prof.  Comstock  regarded  it  as  the  most  destruc- 
tive scale-insect  which  he  had  seen. 

Its  original  home  is  probably  in  China. 

Introduction  into  the  Eastern  States. 

The  scale  was  first  found  in  the  Eastern  States,  in  August, 
1893,  at  Charlottesburg,  Va.  In  March,  1894,  an  infested  locality 
was  found  at  Riverside,  Md.  In  both  cases,  the  introduction  of 
the  insect  was  traced  to  New  Jersey  nurseries,  which  had 
received  the  scale  on  nursery  stock  from  California.  Another 
infested  area  was  discovered  in  March,  1894,  at  De  Funiak 
Springs,  Fla.  Shortly  afterwards  Indiana,  Pennsylvania,  New 
Jersey,  New  York,  Georgia,  Ohio,  Delaware  and,  in  the  summer 
of  1895,  Alabama,  Louisiana,  Connecticut  and  Massachusetts 
were  added  to  the  list  of  infested  states.  At  the  present  time,  the 
San  Jose  Scale  exists  in  nearly  every  portion  of  the  United  States, 
the  extreme  Northern  states  alone,  perhaps,  being  exempt. 

Discovery  and  Spread  in  Connecticut. 

About  twenty  years  ago  the  San  Jose  or  pernicious  scale- 
insect  was  introduced  into  Connecticut  on  nursery  stock  from 
New  Jersey.     It  escaped  notice,  however,  until  June  12th,  1895, 


*  In  1901,  Bulletin  135  was  issued  on  this  subject  but  is  now  out  of 
print.  As  the  control  methods  have  changed  appreciably  since  that  time, 
the  present  bulletin  is  a  revised  and  enlarged  edition  of  the  old,  including 
the  latest  remedies. 


4  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

when  it  was  discovered  at  New  London  by  Dr.  W.  C.  Sturgis, 
botanist  of  this  Station.  The  insect  had  then  been  multiplying- 
for  four  years  in  the  orchard  and  garden  of  Mr.  J.  L.  Raub, 
and  several  trees  had  been  killed  by  it.  A  study  of  the  locality 
was  made  and  a  bulletin  was  issued,  calHng  attention  to  the 
presence  of  the  insect  in  Connecticut,  describing  its  appearance 
and  injuries,  and  giving  the  best  remedies  known  at  that  time. 
(See  Bulletin  No.  121,  July,  1895.) 

Soon  after,  specimens  were  received  from  Hartford  and 
Bridgeport.  During  1896,  additional  centers  of  infection  were 
found  at  Darien,  New  Haven,  Groton,  Mystic,  Farmington,  New 
Britain,  Plantsville,  and  in  the  following  year,  Meriden,  Walling- 
ford,  Hamden,  Woodbridge  and  Greenwich  were  added  to  the 
list.  The  scale  was  found  in  Ivoryton,  Nichols,  Cheshire,  Burn- 
side  and  Rowayton  during  1898,  and  in  several  new  localities  in 
New  Haven,  Hartford  and  Bridgeport.  Previous  to  July  ist, 
1901,  when  the  Insect  Pest  Law  became  operative,  the  San  Jose 
Scale  had  been  found  in  seventy-eight  localities  in  this  State. 

At  the  present  time  it  is  found  practically  all  over  the  State 
and  though  some  orchards  are  still  uninfested,  it  is  doubtful 
if  there  is  a  single  town  or  village  which  does  not  harbor  some 
infested  trees  or  shrubs. 

In  a  few  of  the  places,  the  insect  was  discovered  before  it  had 
infested  more  than  one  or  two  trees.  The  immediate  destruction 
of  these  infested  trees  has  probably  wiped  out  the  pest  from  a 
very  few  localities,  but  in  most  cases  the  scale  had  spread  to  a 
serious  degree  before  it  was  discovered,  and  many  trees  have 
been  killed  and  a  still  greater  number  badly  injured  by  its 
attacks. 

In  the  cities  and  larger  towns  the  scale  has  destroyed  many 
fruit  trees  and  ornamental  shrubs.  A  number  of  large  peach 
orchards  were  ruined  by  it.  Apple  orchards  have  also  been 
severely  injured,  but  the  principal  growers  know  how  to  con- 
trol it  and  do  not  fear  it  as  they  did  a  few  years  ago.  The 
annual  spraying  is  a  part  of  their  orchard  practice  and  no  more 
to  be  neglected  than  cultivation,  pruning  or  fertilizing;  in  fact 
it  is  even  more  important,  as  actual  damage  will  result  if 
neglected. 


the  san  jose  scale  and  methods  of  controlling  it.         5 

Nursery  Inspection  and  Legislation. 

Inasmuch  as  the  San  Jose  Scale  has  been  distributed  chiefly 
by  means  of  nursery  stock,  a  system  of  nursery  inspection  has 
been  established  in  nearly  all  of  the  states.  Previous  to  1896 
several  states  had  passed  laws  requiring  that  each  box  or 
package  of  nursery  stock  shipped  into  those  states  should  be 
accompanied  by  a  certificate  of  inspection  issued  by  a  duly 
authorized   inspector.      States   not  provided   with   an   inspection 


FlG.  2. — Plum  Twigs  nearly  coated  over  by  San  Jose  Scale.     Natural  size. 

system  soon  realized  the  necessity  of  having  one,  both  for  their 
own  protection  and  to  enable  their  nurserymen  to  ship  stock  into 
the. states  where  laws  existed.  Twenty-five  states  had  already 
passed  similar  measures  when  Connecticut,  in  1901,  enacted  an 
inspection  law,  which  was  amended  slightly  in  1903.  At  the 
present  time  forty-five  states  and  territories,  including  Hawaii 
and  Porto  Rico,  have  such  laws,  the  only  ones  without  them  being 
Nevada,  New  Mexico  and  North  Dakota. 


6  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

Though  the  San  Jose  Scale  has  been  the  exciting  cause  of  most 
of  the  legislation,  many  other  injurious  insects  as  well  as  fungous 
diseases  are  debarred,  and  the  inspections  have  prevented  the 
spread  of  a  number  of  very  serious  pests. 

General  Appearance  of  the  Insect. 

Usually  the  insect  appears  upon  the  bark  as  a  greyish,  rough 
coating,  scarcely  noticeable  to  the  naked  eye.  (See  Figures  i 
and  2.)  At  first  there  are  but  few  individuals,  generally  found 
clustered  around  the  buds  and  at  the  branching  of  the  twigs. 
Figure  4  shows  how  the  scales  collect  in  a  groove  or  hollow  in 
one  side  of  a  twig,  as  if  they  had  sought  a  sheltered  situation. 
As  the  trees  become  more  thoroughly  infested,  the  bark  may  be 
completely  covered,  and  sometimes  there  are  several  layers  of 
scales  covering  the  bark.  In  such  cases  leaves  and  fruit  are 
usually  attacked.  The  young  scales  locate  upon  both  sides  of 
the  leaf,  along  the  ribs  (see  Figure  6),  where  they  cause  a  red- 
dish discoloration.  This  discoloration  also  occurs  on  fruit,  and 
on  the  twigs,  especially  where  there  are  but  few  individuals,  and 
it  extends  through  the  bark  to  the  wood.  Where  the  insect  is 
found  upon  the  fruit,  it  seems  to  prefer  the  calyx  and  the  stem 
cavities.  Upon  slightly  infested  trees  the  fruit  is  not  attacked, 
but  on  trees  which  are  badly  infested  the  fruit  is  often  so 
thoroughly  covered  as  to  present  a  very  disgusting  appearance. 
(See  Figures  7  and  8.)  If  we  examine  the  insect  through  a 
pocket  lens,  magnifying  perhaps  ten  diameters,  we  see  that  it  is 
distinctly  circular  in  outline,  somewhat  raised  above  the  bark, 
especially  in  the  center,  where  there  is  a  small  nipple,  differing 
in  color  from  the  other  portion.  If  infested  twigs  are  much 
handled,  the  outer  layer  is  rubbed  away  from  the  nipple,  leaving 
it  a  bright  yellow  color.  Concentric  circles  are  usually  apparent 
between  this  nipple  and  the  outside  edge.  The  scaly  covering 
is  formed  at  the  edge  in  concentric  layers  or  additions.  The 
covering  of  the  male  is  different  in  shape  from  that  of  the 
female.  While  that  of  the  female  is  nearly  circular  in  outline, 
the  armor  of  the  full-grown  male  scale  is  nearly  always  elon- 
gated, with  the  nipple  near  one  end,  and  the  lines  of  formation 
are  eccentric  instead  of  concentric.     (See  Figure  3.) 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  7 

The  color  of  the  shell  or  covering  varies  greatly,  sometimes 
being  a  light  grey,  sometimes  being  nearly  black.  It  frequently 
turns  dark  if  the  insects  are  killed  when  half  grown.  If  killed 
when  fully  grown,  the  shells  often  assume  a  light  grey  color, 


Fig.   3. — San  Jose  Scale  on  peach  twig      a.   mature  female  ;    b.  young 
females  ;    c.   immature  males.     About  twice  natural  size. 


and  finally  drop  from  the  twigs.  If  we  lift  this  shell  or  covering 
with  a  pin  or  point  of  a  knife,  we  will  see  underneath  a  small 
yellow  object,  oval  or  circular  in  outline,  which  appears  like  a  bit 
of  yellow  jelly.  This  is  the  insect  proper  and  is  shown  in  the 
illustration  in  Figure  5. 


8  connecticut  experiment  station  bulletin  165. 

Effect  upon  Trees. 

The  effect  on  the  vitality  of  the  tree  is  not  apparent  until 
the  twigs  become  nearly  covered  by  the  insects.  Then  it  may  be 
noticed  that  the  tree  seems  unthrifty,  but  the  scale  is  so  incon- 
spicuous that  frequently  the  tree  loses  some  of  its  branches  or 
dies  before  the  cause  of  the  trouble  is  discovered.  Frequently 
we  see  a  peach  tree  which  has  been  severely  injured,  and  the 
branches  are  dead,  but  the  trunk  is  still  alive  and  makina^  an 
effort  to  grow  a  new  top.  This  form  of  injury  is  often  seen, 
and  frequently  the  owner  does  not  discover  the  cause  until  his 


Fig.  4. — San  Jose  Scale  on  peach  twig. 
Twice  natural  size. 


Fig.   5. — Female  with  shell  raised  to  show 
insect  beneath.     Much  enlarged. 


trees  reach  this  condition.  The  length  of  time  required  to 
kill  a  tree  depends  on  various  factors.  In  certain  seasons  the 
species  multiplies  much  more  rapidly  than  in  others,  depending 
undoubtedly  upon  the  weather  and  the  abundance  of  natural 
enemies.  The  writer  has  known  of  several  localities  where 
ornamental  plants  were  attacked  and  no  measures  taken  to 
destroy  the  scale,  yet  for  two  or  three  years  the  insect  has  not 
spread  to  any  appreciable  extent.  On  the  other  hand,  in  cer- 
tain orchards,  it  has  spread  with  great  rapidity  in  spite  of 
vigorous  combative  measures.  In  Mr.  Raub's  garden  at  New 
London,  large  peach  trees  were  killed  by  the  scale  in  four  years. 

How  THE  Scale  Spreads  from  Tree  to  Tree. 

The  young  scales  crawl  about  for  a  few  hours  on  the  bark, 
and  if  the  trees  stand  so  close  that  the  branches  interlace,  of 
course  they  can  readily  crawl  from  one  to  the  other.     They  are 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  9 

scarcely  able  to  crawl  long  distances  from  the  trunk  of  one  tree 
to  another  over  the  rough  ground,  but  are  often  blown  about  on 
fallen  leaves  and  may  reach  a  different  section  of  the  orchard 
in  that  way.  In  cultivating  nurseries,  the  workmen  brush  against 
the  young  trees,  and  it  is  quite  possible  for  some  of  the  young 
insects  to  be  carried  to  other  trees  along  the  nursery  rows. 

In  one  case,  the  orchard  became  infested  by  hitching  a  horse 
to   one   of   the   trees,   after   the  team   had   been   in   an   infested 


Fig.   6. — Infested  plum  leaves,   showing  the  tendency  of  the  insects  to 
locate  near  the  veins. 


orchard  three  miles  distant.*  The  throwing  about  of  infested 
fruit  may  aid  in  distributing  the  pest.  Also  where  parings  of 
infested  fruit  are  thrown  out  into  gardens,  there  is  danger  that 
near-by  trees  may  become  infested. 

As  a  rule,  however,  the  insect  is  carried  to  distant  trees  either 
by  other  insects  or  upon  the  feet  of  birds. 


*  Bulletin  No.  3,  New  Series,  Division  of  Entomology,  U.  S.  Department 
of  Agriculture,  Washington,  D.  C,  p.  50. 


lo         connecticut  experiment  station  bulletin  165. 

Life  History  of  the  San  Jose  Scale. 

Both  the  males  and  females  pass  the  winter  in  an  immature 
state,  and  do  not  reproduce  until  the  latter  part  of  June  in  this 
latitude.  The  female  does  not  lay  eggs,  but  brings  forth  living 
young.  The  newly-born  scales  of  both  sexes  crawl  about  for  a 
few  hours  upon  the  twigs.  They  are  provided  with  legs,  eyes, 
antennae  and  mouth-parts.  After  they  have  found  a  suitable 
place,  they  settle  upon  the  bark,  insert  their  beaks  and  begin  to 
suck  the  juice  from  it.  Legs  and  antennae  now  disappear  in  both 
sexes,  and  the  females  lose  their  eyes.    At  first  there  is  a  white 


Fig.   7. — Infested  plums  showing  the  reddish  discoloration  caused  by  the 
insects. 

waxy  substance  exuded,  which  has  somewhat  the  appearance  of 
wool.  A  little  later  this  seems  to  melt  down  and  the  insect  casts 
its  skin.  The  skin,  together  with  the  waxy  substance,  forms  the 
beginning  of  the  shell  or  covering.  After  feeding  for  about 
four  weeks,  the  insect  reaches  the  full-grown  stage.  If  a  female, 
it  then  begins  to  bring  forth  its  young,  continuing  for  a  period 
of  about  six  weeks.  The  number  of  young  produced  by  a  single 
female  varies  from  less  than  one  hundred  in  the  early  part  of 
the  season  to  nearly  six  hundred  in  late  summer.  The  male 
feeds  until  full-grown,  passes  through  the  pupa  stage,  and  finally 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  I  I 

the  adult  comes  forth  from  under  the  shell,  provided  with  eyes, 
wings,  legs,  antennas  and  organs  of  reproduction,  but  with  no 
mouth-parts  nor  digestive  system.  He  can,  therefore,  eat  nothing 
after  reaching  the  adult  stage.  His  only  mission  is  to  mate  with 
the  female  and  die.  The  female,  on  the  other  hand,  after  becom- 
ing established  upon  the  twig,  loses  legs,  antennae,  and  eyes, 
never  again  to  be  possessed  of  these  organs,  while  its  mouth-parts, 
digestive  system  and  reproductive  organs  become  very  strongly 
developed.  It  cannot,  therefore,  move  about,  but  feeds  upon  the 
juices  of  the  plant  and  reproduces  its  kind.  There  are  three 
complete  generations  each  season  in  this  latitude,  and  probably 
four  in  favorable  seasons. 

Food  Plants. 

Though  the  San  Jose  Scale  is  a  pest  chiefly  of  orchards,  it 
must  also  be  taken  into  account  in  the  planting  of  shade  and 
ornamental  trees  and  shrubs,  as  the  cost  of  caring  for  any  exten- 
sive plantation  will  be  much  greater  if  it  has  to  be  treated  each 
year  to  destroy  the  scale. 

In  1902  the  writer  published*  a  rather  extensive  list  of  trees 
and  shrubs,  shoAving  their  susceptibility  to  the  attacks  of  the 
San  Jose  Scale.  Our  experience  since  then  prompts  us  to  make 
a  few  modifications  in  the  hst,  it  being  in  the  main  correct.  The 
following  list  is  really  an  abridged  edition  of  the  former  list, 
with  common  names  used  in  preference  to  Latin  names,  and  most 
of  the  specific  names  have  been  omitted.  It  is  arranged  for  Con- 
necticut, and  may  not  hold  good  for  other  sections  of  the  country. 

List  of  Trees  and  Shrubs  and  their  Susceptibility  to  the  Attacks  of 
THE  San  Jose  Scale. 


Badly  Infested. 

Akebia.  Cherry   (all  kinds  except  sour 

Apple.                                        ■  cherry). 

Apricot.  Choke  berry. 

Basswood  or  Linden.  Cotoncaster  sp. 

Beech,  European   (especially  purple  Currant  (all  kinds). 

.form).  Dogwood       (Cornus      sp.      except 

Buckthorn   (Rhamnus).  florida). 


*  Report  of  this  station  for  1902,  page  132. 


12  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    165. 


Elm. 

Hawthorn   (Crataegus  sp.). 

Hop  tree. 

Lilac. 

Mountain  ash. 

Osage  Orange. 

Peach. 

Pear. 

Photinia  villosa. 

Plum  (all  kinds). 


Poplar  (Populus  sp.). 

Quince    (including  Japanese). 

Rose  (some  hardy  species,  espe- 
cially rugosa). 

Shad-bush  or  June-berry  (Amelan- 
chier). 

Spiraea  {opulifolia,  sorhifoUa  and 
Douglasii). 

Walnut,  Japanese. 

Willow,  several  species. 


Occasionally  Infested,  but  not  Injured. 


Actinidia. 
Alder. 

Almond,  Flowering. 
Ash  {Fraxinus  sp.). 
Birch. 

Bittersweet   (Celastrus). 
Blackberry. 
Box. 

Button     Bush     (Cephalantus    occi- 
dentalism. 
Catalpa. 

Cercidiphyllum  laponicuni. 
Chestnut. 
Dewberry. 

Dogwood,  Flowering. 
Elder  (Sambucus). 
Euonymus  sp. 
Gooseberry. 
Grape  (Vitis). 
Hackberry  (Celtis). 
Honey  Locust   (Gleditschia). 


Honeysuckle  (Lonicera,  some  spe- 
cies). 

Horsechestnut. 

Kieffer  pear. 

Locust  (Robinia). 

Maple  (Acer  sp.)  (especially 
Striped). 

Mulberry. 

New  Jersey  Tea  (Ceanothus). 

Pecan  nut. 

Pepperidge  or  Sour  Gum  (Nyssa). 

Raspberry. 

Rose  (most  species). 

Sassafras. 

Silver  Thorn  (Eleagnus) . 

Smoke  bush  (Rhus  cotinus). 

Sour  Cherry. 

Sumac. 

Viburnum  sp. 

Virginia  Creeper. 

Walnut   (Black  and   Persian). 


Not  Infested. 


Ailanthus. 

Althea. 

Amorpha  fruticosa. 

Androm.eda  sp. 

Arbor-vitcB. 

Baccharis  halimifolia. 

Bald  Cypress  (Taxodium). 

Barberry  (all  species). 

Beech    (American). 

Bladder  nut   (Staphylea). 


Blueberry   (Vaccinium  sp.). 

Boston  Ivy   (Ampelopsis). 

Butternut. 

Buttonwood,  Sycamore   (Platanus). 

Cedar. 

Daphne  sp. 

Deutzia. 

Dutchman's  Pipe   (Aristolochia). 

English  Ivy  (Hedera  helix). 

Filbert  or  Hazel  (Corylus  sp.). 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT. 


13 


Fir  (Abies). 

Forsythia  sp. 

Genista  tinctoria. 

Golden  Chain   (Laburnum). 

Hemlock  (Tsuga). 

Hercules  Club    (Aralia  spinosa). 

Hickory  (except  Pecan). 

Honeysuckle   (most  species). 

Hop-Hornbeam  or  Ironwood 

(Ostrya). 
Hornbeam  ( Carpinus) . 
Huckleberry  (Gaylussacia) . 
Hydrangea    (all  species). 
Hypericum  Moserianum. 
Ilex  sp. 
Itea  virginica. 

Japan  Pagoda  tree   (Sophora). 
Judas  tree  or  Red  bud  (Cercis). 
Juniper. 
Kentucky     Cofifee     tree      (Gymno- 

cladus). 
Koelreuteria  paniculata. 
Larch. 

Leather  leaf   (Cassandra). 
Leatherwood   (Dirca). 
Magnolia   (all  species). 
Maidenhair  tree   (Ginkgo). 
Matrimony  Vine   (Lycium). 
Mock   Orange   or    Syringa    (Phila- 

delphus  sp.). 
Mountain  Laurel   (Kalmia). 
Oak  (all  species). 
Papaw  (Asimina  triloba). 
Paulownia  imperialis. 
Pearl  bush   (Exochorda). 


Phellodendron  sp. 

Pine   (all  species). 

Potentilla  frtiticosa. 

Prickly  Ash   (Xanthoxylum  ameri- 

canum). 
Privet  (Ligustrum  sp.). 
Retinospora   (all  species). 
Rhodotypos  kerrioides. 
Shepherdia  sp. 

Silvet  Bell  (Halesia  tetraptera) . 
Smilax  sp. 
Spice  bush. 
Spruce  (Picea). 
Stephanandra  flexuosa. 
Styrax  japonica. 
Sweet  Pepper  bush  (Clethra). 
Sweet  Gum   (Liquidambar) . 
Sweet-scented    Shrub    (Calycanthus 

floridus). 
Tamarix  sp. 
Trumpet    Creeper     (Tecoma    radi- 

cans) . 
Trumpet  Vine  (Bignonia) . 
Tulip  tree. 
Umbrella    pine    (Sciadopitys   verti- 

cillata). 
Wax  Myrtle   (Myrica  cerifera). 
Weigela. 

White  Fringe   (Chionanthus). 
Wistaria. 

Witch  Hazel   (Hamamelis). 
Xanthcceras  sorbifolia. 
Yellow  Jasmine. 
Yellow  Wood   (Cladastris). 
Yew  (Taxus). 


Natural  Enemies. 

The  native  insect  parasites  of  the  San  Jose  Scale,  Anaphes 
gracilis  How.,  Aphelinus  fuscipennis  How.,  and  Aphelinus 
mytilaspidis  LeB.,  which  have  been  recorded  from  Maryland,* 
are  not  very  effective  in  checking  the  pest  in  Connecticut,  if  they 
attack  it  at  all  here.     In  fact,  at  various  times  we  have  collected 


*  Maryland  Agricultural  Experiment  Station  Bulletin  No.  57,  p. 


14  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    165. 

scale-infested  twigs,  placed  them  in  glass  tubes  and  stuffed  each 
end  with  cotton,  to  see  if  any  parasites  could  be  reared.  None 
were  obtained.  In  examining  orchard  trees  and  inspecting 
nursery  stock  all  over  the  State  we  have  never  observed  anything 
but  slight  indications  that  the  San  Jose  Scale  is  parasitized  in 
Connecticut.  It  is  a  common  occurrence  to  find  old  shells  of  the 
oyster  shell  scale,  each  with  a  small  round  hole  where  the  para- 
site had  emerged.     Not  so  with  the  San  Jose  Scale. 


Fig.   8. ^Infested  Apples  showing  the  discoloration  around  the  insects. 

In  the  South  a  fungus-,  Sphaerostilhe  coccophila,  attacks 
this  as  well  as  other  species  of  scales  native  to  that  region. 
In  Connecticut  a  fungus,  Capnodium,  sp.,  is  often  found  on 
trees  which  are  thickly  covered  with  dead  scales.  This  fungus 
is  evidently  a  saprophyte,  though  partially  parasitic,  and  was  first 
observed  in  1902.* 


Report  of  this  station  for  1902,  p.  129. 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT. 


15 


In  Connecticut  the  most  important  natural  enemies  of  the  scale 
are  predaceous  and  consist  of  two  species  of  lady  beetles  known 
as  the  twice-stabbed  lady  beetle,  Chilocorus  bivulnerus  Muls.,  and 
a  much  smaller  species,  Pentilia  misella  LeC. 


Fig.   9. — The    Twice-stabbed    Lady-Beetle     Chilocorus    bivulnerus    Muls. 
Twice  natural  size. 

The  twice-stabbed  lady  beetle  is  a  moderate  check  on  the  San 
Jose  Scale  in  some  orchards  in  certain  seasons.  We  have 
observed  it  all  over  the  State,  where  it  has  been  found  for  many 


>     IOL: 


^ 


d^  ^•~*^^^  Ji  c 

Fig.  to. — Pentilia  misella  LeC.  a,  beetle  ;  b,  larva;  c,  pupa;  d,  blossom 
end  of  scale-infested  pear,  showing  beetles  and  their  larvse  feeding  upon 
the  scales,  all  greatl)'  enlarged.  (After  Howard  &  Marlatt,  Bull.  3,  N.  S. 
Div.  of  Ent.,  U.  S.  Department  of  Agriculture.) 

years,  and  on  the  whole  it  cannot  be  considered  as  a  very  import- 
ant natural  enem}^  of  the  scale.     It  is  about  three-sixteenths  of 


l6  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

an  inch  long,  and  black,  with  two  red  spots  on  the  back  of  the 
wing  covers.     It  is  shown  in  Figure  9. 

The  other  lady  beetle,  Pentilia  misella,  is  all  black  and  less 
than  one-sixteenth  of  an  inch  long.  We  have  also  seen  this 
species  in  different  parts  of  the  State,  and  sometimes  quite 
abundantly  on  a  few  trees.    It  is  shown  in  Figure  10. 

None  of  the  enemies  mentioned  above  are  important  checks  to 
the  scale  in  Connecticut.  In  fact,  all  of  them  together  do  not 
materially  lessen  the  numbers  of  the  scales,  of  which  from  25 
to  50  per  cent,  are  killed  each  winter,  the  climatic  conditions 
being  a  more  important  check  than  all  insect  and  fungous  enemies 
combined. 

Control  Measures. 

After  more  than  twelve  years  of  experimenting  in  the  Eastern 
States,  the  methods  commonly  practiced  at  the  present  time  are 
fumigating  with  hydrocyanic  acid  gas  to  kill  the  scales  on 
nursery  stock  when  dug  for  shipment  and  spraying  orchard  trees 
with  lime  and  sulphur  mixtures  or  with  oil  preparations. 

Fumigating  Nursery  Stock.* 

Each  well-equipped  nursery  is  now  provided  with  a  tight 
fumigating  house  in  which  hydrocyanic  acid  gas  is  generated 
from  the  chemicals  named  below : 

Quantity  for  Each  100  Cubic  Feet  of  Space — 

1  oz.  (av.)  Potassium  cyanide,  98-100%  purity. 

2  fluid  ozs.  Sulphuric  acid,  high  grade,  66°  Baume  test. 
4      "       "     Water. 

The  fumigating  house  should  be  measured  carefully,  the  cubic 
contents  ascertained,  the  quantities  of  chemicals  computed  and 
the  figures  posted  in  some  place  convenient  for  ready  refer- 
ence. The  house  should  be  as  nearly  square  as  possible,  with 
the  stone  or  earthenware  generating  jar  under  the  slat  floor 
and  near  the  center.  The  loose  trees  should  be  packed  in  hori- 
zontally with  the  roots  outside  and  the  tops  in  the  center.     It  is 


*  For   more    complete    directions    about    fumigating   nursery    stock,    see 
Bulletin  of  Immediate  Information  No.  3  of  this  station. 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  I  7 

imperative  that  the  house  be  suppHed  with  ventilators  and  with 
a  generating  jar  which  can  be  reached  or  operated  from  the 
outside.  The  acid  and  water  should  be  placed  together  in  the 
jar,  stirring  to  prevent  a  too  rapid  generation  of  heat.  Cyanide 
may  be  weighed  out  and  placed  in  cheese  cloth  bags,  and  these 
kept  in  tight  tin  cans  or  glass  jars  ready  for  use.  When  all  is 
ready,  drop  the  cyanide  into  the  jar,  close  everything  tight,  and 
fumigate  for  a  period  between  thirty  and  forty-five  minutes. 
Then  ventilate  the  house  thoroughly  before  entering  it. 

A  house  10  X  lo  x  8  feet  will  be  large  enough  for  most 
nurseries,  contains  800  cubic  feet,  and  for  each  charge  requires : 

Yi  lb.  Potassium  cyanide. 

16  fluid  ozs.   (i  pint)   Sulphuric  acid. 

32      "       "      (i  quart)   Water. 

CAUTION. — Potassium  cyanide  is  one  of  the  deadliest  poisons.  Do 
not  let  it  come  in  contact  with  cuts  or  bruises,  nor  inhale  the  dust  or 
fumes  which  rise  from  it  when  it  is  handled. 

Spraying  Orchard  Trees. 

Orchard  trees  in  the  Eastern  States  are  not  commonly  fumi- 
gated to  rid  them  of  insect  pests  as  are  the  orange  trees  of  Cali- 
fornia. The  expense  would  be  great  on  account  of  their  large 
size.  Considerable  fumigating  has  been  done,  however,  in  Mary- 
land, and  it  has  been  tried  experimentally  in  Connecticut.  The 
common  practice  is  to  spray  the  trees  while  dormant  with  either 
some  form  of  the  lime  and  sulphur  mixture  or  one  of  the  oil 
preparations.  Various  sprays  have  been  developed,  recommended 
and  used.  At  first  whale  oil  soap  was  advised.  Lime  and  sulphur 
was  given  a  trial  by  the  Bureau  of  Entomology  at  Washington 
in  1894  and  pronounced  ineffective,  and  was  not  again  tried  until 
about  1900.  Meantime  kerosene  and  crude  oil  were  used,  the 
latter  tried  extensively  in  New  Jersey,  with  success.  Pumps 
were  devised  for  mixing  oils  with  water  under  pressure,  the 
amounts  being  determined  either  by  different-sized  openings  or 
by  separate  cylinders  of  different  size  or  length  of  stroke.  These 
pumps  are  not  used  extensively  at  the  present  time  because  they 
are  not  to  be  depended  upon  to  give  the  proper  proportions.    If 


1 8  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

the  packing  wears  slightly,  the  proportions  are  changed,  and  in 
practice  it  is  not  uncommon  to  find  the  apparatus  throwing  at 
times  almost  clear  water,  which  will  not  kill  the  scales,  and  at 
other  times  so  much  oil  that  the  trees  are  injured  by  it. 

Various  soap  emulsions  and  rosin  washes  were  tested  and  again 
in  1900  the  lime,  sulphur  and  salt  mixture  was  investigated  and 
made  the  subject  of   extensive   experiments  by  the   Bureau   of 


Fig.  II. — Boiling  the  lime  and  sulphur  mixture.  A  portable  engine  with 
boiler  is  placed  near  the  orchard  where  water  can  be  obtained.  Steam  is 
conveyed  to  the  barrels  through  common  rubber  hose. 

Entomology  and  various  agricultural  experiment  stations  in  the 
Eastern  States.  This  time  better  results  were  secured,  and  the 
work  was  followed  through  several  seasons,  resulting  in  several 
modifications  of  the  mixture,  and  the  best  methods  of  preparing 
it  were  worked  out.  Thus  it  was  found  that  salt  neither  adds  to 
the  effectiveness  nor  the  adhesiveness  of  the  mixture.  New 
York,  New  Jersey,  Maryland,  Georgia,  Illinois  and  Connecticut 
were  some  of  the  states  that  were  foremost  in  the  demonstra- 
tion of  the  practicability  of  the  lime  and  sulphur  mixtures  in  the 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT,  I  9 

East  and  the  development  of  the  formulas  for  preparing  them. 
Some  of  the  methods  of  making'  without  boiling  are  not  now  in 
vogue  because  of  the  commercially  prepared  mixtures  that  are 
now  on  the  market.  The  development  and  perfecting  of  the 
"soluble"  or  miscible  oil  mixtures  during  the  past  few  years  has 
enabled  us  to  spray  with  an  ordinary  pump  oil  emulsions  which 
can  be  readily  diluted  with  water.  These  have  in  part  supplanted 
the  use  of  the  lime  and  sulphur  mixtures,  though  after  using 
them  many  commercial  orchardists  are  now  returning  to  the  lime 
and  sulphur  preparations,  especially  for  peach  trees,  on  account 
of  their  great  fungicidal  value.  The  home  preparation  of  the 
"soluble"  or  miscible  oils  has  been  worked  out,  but  this  is  too 
complicated  for  general  practice,  and  we  do  not  advise  it  except 
in  the  large  orchard  where  materials  can  be  purchased  in 
quantity.  Even  then  it  will  often  be  found  cheaper  to  pay  the 
manufacturer  for  mixing,  and  a  more  uniform  product  will  be 
obtained. 

Homemade  Lime  and  Sulphur  Mixtures. 

For  making  the  regular  boiled  mixture  we  use  fresh  white- 
wash or  finishing  lime,  nearly  free  from  magnesia,  and  finely 
ground  sulphur  known  as  light  sulphur  flour  or  the  subHmated 
product  called  flowers  of  sulphur.  The  boiling  may  be  done  in 
a  kettle  over  a  fire  or  in  an  open  barrel  with  steam  from  a  boiler, 
as  is  shown  in  Figure  ii.    We  advise  the  following  proportions: 

20  lbs.     Lime. 
14  lbs.     Sulphur. 
40  gals.  Water. 

The  lime  should  be  started  slaking,  then  add  the  sulphur  and 
with  constant  stirring  add  enough  water  to  cover,  and  boil  for 
about  one  hour.  Then  strain  into  the  pump  barrel  and  dilute 
with  cold  water  to  make  forty  gallons.  The  mixture  should 
then  be  applied  at  once  to  the  dormant  trees.  If  allowed  to  stand 
over  night,  crystals  form  in  the  bottom  of  the  barrel  which  clog 
pump  and  nozzles,  and  it  is  necessary  to  heat  it  up  again  before 
using. 

There  are  several  formulas  for  making  the  mixture  without 
boiling,  but  the  space  here  is  too  limited  to  discuss  them.     In 


20  CONNECTICUT   EXPERIMENT    STATION    BULLETIN    165. 

general,  we  advise  the  orchardist  either  to  make  the  boiled  mix- 
ture or  to  purchase  the  ready-prepared  commercial  mixture 
which  is  now  sold  on  the  market — a  brand  being-  made  by  nearly 
every  manufacturer  of  insecticides. 

Commercial  Mixtures  of  Lime  and  Sulphur. 

For  the  last  two  years  a  number  of  different  makes  of  lime- 
sulphur  mixtures  have  been  made  and  sold.    We  have  not  tested 


Fig.   12. — An  excellent  outfit  for  a  rough  orchard  is  shown  at  the  right. 

them  all,  but  some  of  them  have  been  used  by  us  and  also  in 
large  quantities  by  Connecticut  orchardists.  The  results  have 
been  satisfactory.  Such  preparations  are  clear  liquids  of  amber 
color.  The  sulphur  is  all  dissolved,  no  crystals  form  on  standing, 
and  there  is  no  sediment  to  clog  pumps  and  nozzles.  It  is  only 
necessary  to  dilute  nine  or  ten  times  with  water,  according  to 
directions.  It  can  be  purchased  in  any  quantity  from  one  gallon 
up  to  a  car  load  lot,  and  is  less  expensive  than  most  of  the  oil 
preparations  and  only  slightly  more  so  than  the  homemade  lime- 
sulphur  mixture. 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  21 

Lime  and  sulphur  mixtures  may  be  applied  to  the  dormant  trees 
any  time  between  November  ist  and  April  15th  in  Connecticut, 
and  there  is  no  danger  whatever  of  injuring  the  trees.  It  is  an 
excellent  fungicide,  the  best  remedy  for  peach  leaf  curl,  and 
by  still  further  dilution,  say  thirty  times,  the  commercial  prepara- 
tions are  recommended  for  use  as  a  summer  fungicide  spray. 

"Soluble"    or  Miscible  Oils. 

Several  preparations  of  this  type  are  on  the  market,  "Scale- 
cide"  being  one  of  the  oldest  and  best  known.  These  oil  pre- 
parations are  really  emulsions  and  most  of  them  contain  a  vege- 
table oil  and  an  alkali  which  when  mixed  together  with  mineral 
oils  in  the  right  proportions  will  hold  the  latter  as  an  emulsion 
when  diluted  with  water.  Some  also  contain  fish  oil  and  carbolic 
acid.  Those  who  wish  to  make  up  their  own  miscible  oils  should 
consult  the  publications  of  Penny*  and  Jarvisf  and  the  report 
of  this  station  for  1908,  page  837,  but  the  average  orchardist  had 
better  purchase  a  ready-made  oil  mixture  than  to  attempt  to 
make  it  himself.  With  all  oil  preparations  there  is  more  or  less 
separation  of  the  ingredients  on  long  standing,  so  that  the 
entire  contents  of  each  original  package  should  be  mixed  very 
thoroughly  before  any  portion  is  removed  to  mix  with  water. 
If  this  is  not  done,  the  oil  preparation  will  not  mix  properly  with 
water  and  is  liable  to  injure  the  tree. 
Never  use  any  miscible  oil  preparation  that  refuses  to  mix  with,  water. 

Lime  and  Sulphur  Mixtures  vs.  Miscible  Oils. 

The  advantages  of  the  lime  and  sulphur  mixtures  are  the 
cheapness,  effectiveness  in  killing  scales  and  excellent  fungicidal 
quahties.  If  the  bark  has  been  well  coated  with  this  mixture 
the  scales  do  not  become  established  upon  it  the  following  season 
as  readily  as  when  the  oil  mixtures  are  used.  There  is  no  injury 
to  the  trees,  and  the  rubber  hose  is  not  ruined. 


*  Bulletins  Nos.  75  and  79,  Delaware  Agricultural  Experiment  Station, 
1907.     Bulletin    No.    86,    Pennsylvania    Agricultural    Experiment    Station, 


t  Bulletin     No.     54,     Storrs     (Connecticut)     Agricultural     Experiment 
Station,  1908. 


2  2  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

The  disadvantages  are  that  it  is  caustic  and  somewhat  unpleas- 
ant to  handle,  and  if  the  spray  strikes  the  light-colored  paint 
of  a  fence  or  building  it  discolors  it,  forming  black  spots,  which 
disappear  after  a  few  weeks.  It  gives  the  trees  a  whitish  color, 
slightly  disfiguring  them.  Its  penetrating  qualities  are  not  as 
great  as  in  the  oil  preparations,  and  on  old  apple  trees  having 
much  rough  bark  the  latter  are  often  preferable.  The  pubescent 
terminal  twigs  of  the  apple  also  can  be  covered  more  readily 
with  the  oils  than  with  the  lime  and  sulphur,  which  tends  to 
gather  in  drops  and  roll  off.  Where  apple  trees  are  sprayed 
with  the  lime  and  sulphur  mixture  it  is  a  common  experience 
to  find  no  scales  on  the  old  wood  but  enough  on  the  new  twigs 
to  infest  the  fruit  and  spot  it  noticeably.  The  lime  and  sulphur 
mixture  corrodes   slightly  the  metal  parts   of  the  pumps. 

Advantages  of  the  oil  preparations  are  that  they  are  pleasant 
and  not  caustic  to  handle,  and  will  not  disfigure  the  trees,  shrubs, 
or  painted  buildings.  They  do  not  clog  or  corrode  pumps  or 
nozzles,  and  they  penetrate  nicely.  A  gallon  will  cover  more 
surface  than  a  gallon  of  lime  and  sulphur. 

Disadvantages  are  that  the  ingredients  separate  on  standing 
and  evaporation  sometimes  prevents  the  proper  mixing  with 
water.  Injury  has  been  caused  to  trees  by  the  use  of  such  prep- 
arations not  properly  mixed.  Scales  will  set  more  readily  on 
the  bark  after  the  use  of  the  oil  mixtures  than  where  lime  and 
sulphur  is  used.  It  is  more  expensive  and  is  not  as  valuable 
as  a  fungicide.  The  oils  affect  rubber,  and  the  hose  is  quickly 
ruined. 

How  TO  Treat  an  Infested  Orchard. 

Suppose  we  have  a  badly-infested  orchard  of  peach  or  apple 
trees,  how  shall  we  treat  it?  This  is  a  problem  confronting 
many  commercial  fruit-growers  in  Connecticut  to-day,  as  well 
as  a  large  number  of  persons  who  have  small  orchards  for  the 
home  supply. 

In  the  light  of  our  present  knowledge  of  what  has  been  accom- 
plished in  Connecticut  and  elsewhere  the  following  treatment 
seems  to  be  the  proper  one  to  apply. 

Remove  the  worthless  trees.     It  will  not  pay  to  treat  them. 


THE  SAN  JOSE  SCALE  AND  METHODS  OF  CONTROLLING  IT.  23 

Cut  back  severely,  especially  the  branches  that  have  lost  a  por- 
tion of  their  vitality  because  infested.  This  will  enable  the  trees 
to  make  a  stronger  growth  in  the  spring  and  reduce  the  area  to 
be  covered  with  the  spray.  The  remaining  portion  being  nearer 
the  ground  can  be  sprayed  more  economically  than  the  ends  of  the 
twigs.  Burn  all  branches  cut  off;  fire  is  an  effective  destroyer 
of  insects  and  fungous  diseases. 


Fig. 


-Outfit  mounted  on  waggon. 


Spray  the  pruned  trees  during  the  winter  months  with  the 
lime  and  sulphur  mixture,  or  one  of  the  miscible  oils,  taking 
pains  to  coat  thoroughly  all  portions  of  the  trunk  from  the 
ground  to  the  ends  of  the  branches. 

Peach,  plum  or  pear  trees,  which  have  smooth  bark,  should 
be  sprayed  with  lime  and  sulphur,  which  kills  the  scale  and  is 
also  a  good  fungicide ;  oil  preparations  are  often  preferable  on 
rough-barked  apple  trees.  Badly  infested  trees  sometimes  need 
to  be  sprayed  twice  the  first  season,  in  which  case  the  oil  may 
be  applied  in  November  as  soon  as  the  leaves  fall  and  lime  and 
sulphur  in  the  spring.     The  oil  mixtures  should  be  diluted  with 


24  CONNECTICUT    EXPERIMENT    STATION    BULLETIN    165. 

not   more   than    fifteen    parts    water.      Both    lime    and    sulphur 
mixtures  and  oil  preparations  may  be  used  in  the  fall. 

When  growth  begins,  fertilize  liberally,  spray  apple  trees  to 
preserve  the  foliage,  and  cultivate  thoroughly  to  promote  the 
vigor  and  health  of  the  trees. 

SUMMARY. 

The  San  Jose  Scale  appeared  and  caused  much  destruction  of  fruit  trees 
in  California  thirty  years  ago.  China  is  probably  the  country  of  its 
origin. 

It  was  first  found  in  the  Eastern  States  in  1893,  and  now  occurs  in 
nearly  all  the  states  of  the  Union  except,  perhaps,  the  extreme  northern 
ones. 

The  scale  was  brought  into  Connecticut  on  nursery  stock  in  the  early 
nineties,  but  not  discovered  until  1895.  Seventy-eight  infested  localities 
had  been  found  in  this  State  and  twenty-five  states  had  passed  inspection 
laws  up  to  July  ist,  1901,  when  the  present  Insect  Pest  Law  went  into 
effect.  Since  that  time  the  scale  has  spread  to  nearly  every  portion  of 
the  State  and  forty-five  states  and  territories  now  have  laws  regarding 
the  inspection  and  transportation  of  nursery  stock. 

The  scale  is  inconspicuous  and  is  seldom  noticed  until  the  vitality  of 
the  tree  is  impaired,  at  which  time  the  bark  is  usually  coated  with  a 
roughish  grey  substance.  The  reddish  discoloration  may  be  found  around 
each  individual.  Leaves  and  fruit  are  also  attacked.  The  female  scale 
is  nearly  circular  in  outline,  while  the  male  is  somewhat  elongated.  If 
the  scale  is  lifted  the  insect  proper  may  be  seen  underneath,  by  the  aid  of 
a  lens,  as  a  yellow  object. 

The  vitality  of  the  tree  is  gradually  lessened  by  the  hordes  of  insects 
sucking  its  sap.  The  pest  is  seldom  noticed  until  some  of  the  twigs  die. 
Entire  trees  have  been  killed  in  four  years  in  Connecticut  by  the  scale. 

Though  the  young  scales  crawl  short  distances,  they  are  usually  carried 
from  one  tree  to  another  by  other  insects,  or  upon  the  feet  of  birds.  They 
may  also  be  carried  upon  fallen  leaves,  fruit,  or  the  clothing  of  persons,  etc. 

The  full-grown  female  scale  gives  birth  to  living  young,  w^hich  crawl 
about  for  a  short  time  and  then  settle  upon  the  bark.  There  are  three  or 
four  generations  each  season.  They  feed  by  sucking  the  juices  from  the 
tree.  Each  female  may  produce  from  less  than  one  hundred  to  six  hundred 
young. 

Common  fruit  trees  and  plants  of  the  rose  family  are  usually  preferred 
by  the  insect,  but  it  is  liable  to  attack  other  kinds  that  may  be  growing 
near  infested  trees.     A  list  of  food  plants  may  be  found  on  page  11. 

Natural  enemies  are  not  very  effective  in  holding  the  scale  in  check  in 
Connecticut,  the  most  important  being  twro  species  of  lady  beetles. 

In  nurseries  the  stock  is  fumigated  with  hydrocyanic  acid  gas  when  dug 
for  shipment.  Orchard  trees  are  sprayed  while  dormant  with  the  lime 
and  sulphur  mixture,  or  with  one  of  the  "  soluble  "  or  miscible  oils  diluted 
at  the  rate  of  one  part  in  fifteen  parts  of  water. 


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